Editor's Note: The following message was posted to the SETI Email Discussion List on 22 August 1997. It documents one member's thoughts and efforts, and is reproduced here to help others grapple with the many decisions involved in building a working SETI station. As Dick's station begins to take shape, we hope to update this page.

Greetings everyone,

I am finally starting work on my Radio Telescope after 2 years of
procrastination. So far the only progress made is a section of Rohn
25G in about 2 square yards of concrete for my 10' TVRO dish. Perhaps
my procrastination is going to have some benefits. Over the last 2
years, I've read every book & article relating to radio Astronomy and
SETI that I could find. I've joined the SETI League and the Society of
Amateur Radio Astronomers (SARA). In 1996, I made the trek to the
National Radio Astronomy Observatory (NRAO) in Green Bank, West
Virginia with the SARA group and actually met Grote Reber (the father
of Radio Astronomy). I also got to "play" with a 40 foot Radio
Telescope and saw the 150 foot scope demonstrated by visiting
astronomers. Yes _ with a 150 foot scope, the "bump" of the Hydrogen
line is very apparent on a spectrum analyzer. I also met Paul Shuch
for the first time and heard his presentation on SETI. I was impressed
enough with Paul to ask him to speak at a Banquet & Seminar given by
our local Amateur Radio Club, The Keystone VHF Club, in York,
Pennsylvania. Paul graciously accepted our invitation, and stimulated
the imaginations of over 50 members of our club_ that's just about the
most people I've ever been able to get together for any event from our
organization.

Since then, I've scoured the Internet for information and have
been a subscriber to this reflector for the last 6 months. I've been
exposed to many points of view and have found the multitude of
opinions & ideas enlightening. I finally feel that I am armed with
enough knowledge to "be dangerous".

My idea for a Radio Telescope is to use as many "off the shelf"
components as possible. Build where necessary, but don't re-invent.
The basis for my scope' is an existing 10 foot TVRO dish that I've
owned for the last 11 years (we finally got the cable).

The Dish - With a little help from a friend with a welder, I am
modifying the existing mount so that the positioner arm drives the
dish in elevation (rather then along the Clark belt). Basically, this
mod entails rotating the mount about 90 degrees and welding a metal
plate on the back. Three heavy duty U-bolts will be placed in the
metal plate to hold the mount to a thick walled 2 ½" steel pipe. This
pipe will extend 10 feet into the Rohn 25 with only a 18 inches or so
coming out of the top of the tower section. There will be two thrust
bearings in the tower section, one at the top where the pipe comes
out, and one near the bottom. While this may not seem heavy duty
enough for some of you, the pipe only extends from the tower a short
distance, it should be able to take quite a bit of bending torque
without being damaged. The whole works is also in a location fairly
well protected from high winds. Rotating this pipe will move the dish
in azimuth.

For the drive, I have procured a heavy duty electric motor
with an integral gearbox. The motor runs on a DC from about 3V to 9V.
At it's highest speed, it turns about 1 RPM. I was intending to couple
this to the pipe through a heavy duty 11 to 1 ratio gear box and
chain/sprocket. I currently have all of these materials but am
rethinking this process. I am wondering if perhaps a propeller pitch
motor coupled directly to the bottom of the pipe might not be simpler
and more robust. With this two axis drive system in place, I can move
the dish to any point in the sky desired. Since my positioner arm for
elevation has a sensing potentiometer in it (not a reed switch), I
can get elevation read out directly in the shack. I will have to mount
& couple a potentiometer to the pipe to get position back for azimuth.
I also have a TAPR Track box and the Kansas City Tracker that I hope
to integrate with this system for automatic pointing. I feel that the
dish mounting is going to be the hardest part of the whole project.
While a simple stationary Drift Scan mount would suffice, I like the
idea of being able to look at one spot in the sky for an extended
period of time when desired.

The Feedhorn - Jeffrey Lichtman of Radio Astronomy Supplies currently sells a linear polarized 1.420 Ghz
feedhorn with a choke ring. It also includes an N-fitting for output.
I should be able to modify the existing C-band LNB mount to support
this with little effort. The price for SETI League members is $150 and
$160 for others. You can check out Jeffrey's home page at
http://www.nitehawk.com/rasmit/ras.html.

The LNA - We have a couple of choices here (probably even more).
Jeffrey Lichtman has a two stage LNA with a gain of 28 dB and a noise
figure of .35 dB that looks interesting, price is $180. Down East
Microwave also has a comparable amp that is a few dollars cheaper. Has
anyone had experience with these devices? Opinions? Probably a strip
line filter on the input would be desirable but will raise the noise
figure. I live "in the boonies" so I hope to get away with no
filtering.

The feedline - While probably not necessary, I am going to use 7/8"
hardline back to the shack (I already have it). The run will be about
80 feet. I am also going to power the LNA with a separate wire rather
then trying to decouple through the hardline.

The Power divider - Upon entering the shack with the feedline, I'm
going to try something a little different. Since I want to do some
Radio Astronomy as well as SETI, I am going to attempt to drive two
separate receive systems. I will be building the power divider
myself. It will be frequency selective but should cover everything
near the Hydrogen line.

Receiver #1 - For radio Astronomy a wide receive bandwidth is
necessary. There is a small company called Science Workshop that makes
what is known as "The Poor Man's Spectrum Analyzer". While their
analyzer lacks the calibration accuracy of the multi thousand dollar
units, it covers from below 100 Mhz all the way through 1.7 Ghz with a
sensitivity just about as good as it's expensive HP cousins. You have
to supply an inexpensive Oscilloscope (freq response < 100 Khz) for
the display. As well as serving as a Spectrum Analyzer, the ramp
generator may be switched off and this analyzer will serve as a wide
band receiver tunable throughout the same frequency range. It is not
super stable in frequency for narrow band signals (eg: 5Khz FM). If I
tune in a local 2 meter repeater, it eventually drifts out of the
passband. The thing is, it's not meant for high performance narrow
band reception, it's a Spectrum Analyzer, and it does that job well!
It also will serve quite well in the capacity of a wide band receiver
(<250Khz bandwidth). If you take the IF outputs of the Varactor tuners
and drive a detector circuit, and then from that, a sensitive DC
amplifier, followed by a Strip Chart Recorder (or a computer A/D
converter) _. Bingo, an instant Radio Astronomy receiver tunable
anywhere between below 100 Mhz through 1.7 Ghz. Want to try and see
the bump on the Hydrogen line? You even have a Spectrum Analyzer to
make the attempt!

You can also use this device to do Radio Astronomy at
C-Band frequencies. Keep your existing C-Band LNB powered up and drive
the analyzer with it's output. Since the TVRO satellite 3 Ghz outputs
are all downconverted to about 950-1500 Mhz, you will be effectively
be looking at the entire satellite C-band spectrum, if you are aimed
at a TVRO satellite, you will see data from all of it's transponders.
If you are looking away from the Clark Belt, you will be looking at a
chunk of the sky with a wide band receiver!
This little gem is available from Science Workshop located in
Bethpage, New York (516) 796-1693, WEB:
http://www.science-workshop.com. The price will amaze you, it kit
form, you can build the complete unit for less then $250. I've had
mine for over 10 years now and I'm upgrading it for up to 1.7 Ghz
operation. Check out Science Workshop's WEB page!

Receiver #2 - For SETI, narrow bandwidth and good frequency stability
is necessary. With the availability of computer programs such as
Mike Cook's FFTDSP and Dan Fox's SETIFOX that do Fast Fourier
Transformations to detect coherent signals under the noise, receiver
drift cannot be tolerated. For this reason, I await with baited breath
the release of the SETI League's 1420 Mhz receive converter from Down
East Microwave. This is crystal controlled and has an advertised noise
figure of approximately 1.5 dB. It's IF output is on the 4 Mhz of the
2 Meter Amateur band. Using this converter will allow your existing 2
Meter all mode receiver to provide plenty of selectivity and certainly
serve as a good I.F. amp. I was even thinking about using the
downconverter as a wide band receiver for Radio Astronomy but with
the IF output in the 2 meter band, the potential for interference is
great, especially if I am trying to listen to something over 250 Khz
wide! Price in kit form should be around $130.
Hopefully, I will be able to run both of these receivers at the same
time off the outputs of the power divider. With 28 dB of gain from
the LNA and 7/8" hardline, I shouldn't need any post amplification. My
main concern is RF from either receiver getting into the other.

Signal Processing - I am currently using Mike Cook's software
FFTDSP42u for audio processing. I also have a 8 bit A/D converter
connected to my PC and am using a package called "Datalog" that I
obtained from Radio Astronomy Supplies. This makes very nice strip
charts and also creates a text file of the sampled data that is easily
imported into a variety of database programs and spreadsheets. I have
used Mike's FFTDSP to detect the Mars Global Surveyor during the Mars
Relay Flight Test. I also use it to look at the Philadelphia 432 Mhz
CW beacon. This beacon is located about 100 miles from my location and
, Mike's software clearly shows reflections of this signal off
aircraft with the associated Doppler. I've used the Datalog software
for a variety of purposes; from logging enhancements on 2 meters & 70
CM to plotting signal strength profiles of high altitude balloons
carrying Amateur Television (ATV) from over 400 miles away.

While I have a good bit of the hardware/software necessary for this
project, I'm sure that I'll run into some set backs. My first priority
is to get the dish re-mounted before the onset of Winter, after that I
can put the other stuff together even with a foot of snow on the
ground. Some questions that I have are:

Does anyone have access to Propeller Pitch motors?

Other ideas on mounting the dish?

Ideas on how to bring dish positional data back to the shack?

Has anyone used the Poor Man's Spectrum Analyzer for Radio Astronomy?

How about some opinions on different LNA's ?

Finally in the software wish list category, is anyone aware of any
program that controls the Kansas City Tracker/Track Box in Right
Ascension & declination? For example, FFTDSP will display in real time
the azimuth & elevation of a point in space if the RA and declination
is entered. This positional data could then be used to drive the KCT.
That's about it. Hopefully this is a reasonably realistic approach
to putting together a Radio Telescope. As I progress, I'll list my
successes & failures here.